"Hyperbola: Under Construction!" by Mark Frantz, (November): Geometer's SketchPad files.
"A Topological Definition of Limits for Use in Elementary Calculus" by Charles L. Cooper, (September): Topological Limits (pdf).
For "Locating Unimodular Roots" by Michael A. Brilleslyper and Lisbeth E. Schaubroeck, (May): This Mathematica notebook gives dynamic recreations of some results from the article and outlines explorations of additional related topics.
For "Integer Solutions to Box Optimization Programs" by Vincent Coll, Jeremy Davis, Martin Hall, Colton Magnant, James Stankewicz, and Hua Wang (May): The following Sage code generates rational solutions to the box problem described in the article. For more information, see stankewicz.net/optimization.html.
def _(n = 12):
assert type(n) == Integer
m = kwargs['m']
ell = implicit_plot(x^2 - x*y + y^2 ==1,(x,-2,2),(y,-2,2))
pt1 = point((-1,0),pointsize=80,rgbcolor=(1,0,0))
pt2 = point(((-(m/n)^2 + 1)/((m/n)^2 - (m/n) + 1),(-(m/n)^2 + 2*(m/n))/((m/n)^2 - (m/n) + 1)),pointsize=80,rgbcolor=(1,0,0))
pt3 = point((0,(m/n)),pointsize=80,rgbcolor=(0,0,0))
line = plot((m/n)*(x+1),(x,-2,2),color='green')
show(ell + pt1 + line + pt2 + pt3)
print "t = "+str(m/n)
print "x = "+str(n^2 - m^2)
print "y = "+str(2*m*n - m^2)
print "z = "+str(m^2 - m*n + n^2)
print "Roots = "+str((m*n - m^2)/2)+", "+str((2*n^2 + m*n - m^2)/6)
2013, Volume 44
For "Collaborative Understanding of Cyanobacterial Growth in Lake Ecosystems" by Meredith Greer, Holly A. Ewing, Kathryn L. Cottingham, and Kathleen C. Weathers (November) Data for Gloeo Modeling (xlsx).
For Kenneth Schilling's "Derivative Sign Patterns in Two Dimensions" (March) Web Addendum (pdf).
2012, Volume 43
For Timothy Jones' "Euler's Identity, Leibniz Tables and the Irrationality of Pi" (November): End Notes (pdf)
2011, Volume 42
For Stephen M. Walk's "The Intermediate Value Theorem is NOT Obvious—and I AM Going to Prove It to You" (September): Proofs Leading to the Intermediate Value Theorem (pdf)
For Michael A. Jones' "Chutes and Ladders for the Impatient" (January), MAPLE file.
2010, Volume 41
For Richard Kreminski's, "Taylor’s theorem: the elusive c is not so elusive" (May): Proofs of Theorems 2 and 3, plus other materials(pdf)
For Rick Mabry’s "The Hardest Straight-in Pool Shot" (January), proofs of all nine FACTS, written on napkins. Separate napkins (pdfs):
All the napkins in one wad: Facts 1-9
2009, Volume 40
For Barry Cox and Stan Wagon’s "Mechanical Circle-Squaring" (September, pp 238-247), Mathematica generated simulations:
Geneva Drive Maltese Cross
Drilling a Square Hole
Drilling a Square Hole (Three Dimensions)
Drilling a Hexagonal Hole